Songbird , here we go again :
A bit more in depth this time.
On the delay :
Yes, several seconds, but always better than the average 29
.
Problem is that ATC using radar always look at the past. whether it is, 4, 9 or 12 seconds. TCAS is a very dynamic system, which can issue corrective RAs and whose version 7 can even issue corrective reversal RAs. Those, in order to be effective have to be followed by pilots within 2.5 seconds according the manufacturer manuals. We agree so far right ?
My point :
This will only happen in some particular situations, I agree, but in a mode S download situation what will be displayed to the controller on his screen will be totally different of what is happening in real time, hence increasing the possibility /likelihood of controller intervention.
On the technical downlink medium :
So, connect the downlink to those RA's which are displayed in the cockpit. Problem solved.
This will mean re-encoding the displayed RAs and re-broadcasting them .I am not an engineer, but this will be complex and possibly expensive , and adding an avionic box is not the idea.
Also in Eurocontrol they have already decided that should we go for RA downlink , it ill be using the mode S broadcast. The cost of using the other (better) method of using the 1090 Extended squitter was judged prohibitive for that function only.
Replying to your question :
it is not clear to me wether the '70 % more or less correctly' is of the total population, or only of the 10% that remains. If the latter is the case, then, logically, the real problem is only for 3 % of the TCAS total?
The 70% is within the initial 10% which are valid correct RAs. The rest is raw data , you cannot start to make percentages values on unvalidated data !
Increasing Controller involvement 2 :
I don't think your statement is supported by the downlink simulations which were organized in Bretigny.
Be careful in analyzing the outcome RADE simulations. the rather large RADE 1 was only a simulation on the HMI ( i.e the display) of RAs, and indeed most controllers there found the HMI adequate.
The 3 subsequent low-scale RADE simulations start to show another picture, and the 4th one ( RADE2T, only with 4 controllers from 2 APPs ) show the real limitations. The number of RAs shown to controller during those simulation was so low that I would refrain from drawing firm conclusions one way or another.
What I myself found interesting (and worrying),in those simulations is that despite this simulated environment, and the low numbers, on 2 occasions controllers intervened after an RA ! Training is still a major issue, also for controllers..
On the safety nets :
STCA (short term conflict alert, the ATC safety net) is only a safety net. I'm sure all area controllers take it into consideration when they work (admittedly, provided the number of false alerts is reasonable, but if this is the case management and technical staff should urgently repair the tool). Why should TCAS, as you say equally 'only a safety net', be treated differently when this is made possible?
Ah, the old discussion between a safety tool and a safety net !
We could debate this for hours,. Short version : NO controllers should not use STCA and TCAS as safety tools. ( and they are trained and told not to )
Finally :
(what has the FAA to do with Europe, but that's another matter, I would think worldwide ICAO is the Ageny to address),
The FAA owns the TCAS system . Changes to its software and procedures have to be discussed with them trough RTCA. It is not a European system. ICAO do only issue SARPs for ACAS . They have no influence on TCAS.( and frankly no expertise either )
As an aside, I do not represent or talk for IFATCA here, but it happens that I agree with what they say on this particular point , which also happens to be very close to what the IFALPA ATS committee says by the way.
In a nutshell : No against Downlinking of RAs per se , but not now. Solve the problems first to make sure we will not add more problems than we want to solve, and increase, not decrease the likelihood of controller intervention .
Absolutely against introducing it now here and there to " see what happens" and " gain experience " etc...